Core-shell type polymer particle, aqueous polymer emulsion, and hair cosmetic composition

ABSTRACT

The present invention relates to a core-shell type polymer particle including a shell part composed of an amphoteric polymer (A) and a core part composed of a hydrophobic polymer (B).

TECHNICAL FIELD

The present invention relates to a core-shell type polymer particlewhich is, for example, used as an emulsion for cosmetics, an aqueouspolymer emulsion having the core-shell type polymer particle dispersedin water, and a hair cosmetic composition including the polymer emulsionblended therein.

BACKGROUND ART

It is well known that the hair is fixed with a resin to give a desiredshape. As such a resin for cosmetics, various ionic polymers inclusiveof anionic polymers, for example, acrylic, vinyl acetate-based,vinylpyrrolidone-based, or vinyl methyl ether-based polymers, aregenerally known. Films formed of such a resin are usually hard andbrittle, so that they are insufficient in flexibility and involve suchan aspect that a finish feeling of the hair is stiff, and a naturaltexture is failed.

In particular, when it was intended to enhance a hairdressing effect,the results that the film becomes harder, thereby more deteriorating thefinish feeling of the hair were brought. In addition, cationic acrylicpolymers, vinylpyrrolidone-based polymers, or vinyl methyl ether-basedpolymers become very flexible at the time of high temperature and highhumidity, thereby easily causing a sticky phenomenon, and also thehairdressing effect tends to be lowered. In addition, because of poorslippage of the film, a touch feeling of the hair was also not good.

As for materials capable of improving these defects of resins,amphoteric macromolecular polymers having flexibility of film aredescribed in Patent Literatures 1 to 3. Furthermore, as for materialscapable of more improving the slippage of films, a hair cosmeticcontaining an acrylic-urethane emulsion described in Patent Literature 4is known.

BACKGROUND ART LITERATURE Patent Literature

Patent Literature 1: JP-A-S49-14647

Patent Literature 2: JP-A-S51-9732

Patent Literature 3: JP-A-S55-104209

Patent Literature 4: JP-A-2007-001969

SUMMARY OF INVENTION Technical Problem

However, when the polymers or emulsion described in the above-describedliteratures are used for a hair cosmetic, although the flexibility canbe improved, there is such a problem that a setting power or humidityresistance is lowered. In addition, although many of conventionalpolymers used for a hairdressing agent or the like are usuallysufficient in the hardness and setting power, the softness of the touchfeeling is therefore sacrificed, and there is such a problem that thecompatibility between hardness and softness is insufficient.Accordingly, the development of, as a polymer to be used for ahairdressing agent or the like, a resin having not only flexibility,suppleness, and softness but also humidity resistance and a settingpower is demanded.

An object of the present invention is to solve the above-describedproblems and to provide a core-shell type polymer particle not onlyhaving hardness, softness, and humidity resistance but also beingcapable of forming a film which is easily washed and removed, an aqueouspolymer emulsion, and a hair cosmetic composition.

Solution to Problem

In order to achieve the above-described object, the inventors of thepresent invention made extensive and intensive investigations. As aresult, it has been found that a specified core-shell type polymerparticle composed of an amphoteric polymer and a hydrophobic polymer notonly has hardness, suppleness, softness, and humidity resistance butalso makes it possible to form a film that is easily washed and removed,leading to the present invention. Specifically, the gist of the presentinvention resides in the following [1] to [10].

[1] A core-shell type polymer particle comprising a shell part composedof an amphoteric ion polymer (A) and a core part composed of ahydrophobic polymer (B).

[2] The core-shell type polymer particle according to [1], wherein theamphoteric polymer (A) contains a repeating unit derived from anunsaturated monomer having a betaine structural group.

[3] The core-shell type polymer particle according to [1], wherein theamphoteric polymer (A) contains a repeating unit derived from anunsaturated monomer having an amine oxide group.

[4] The core-shell type polymer particle according to [1], wherein theamphoteric polymer (A) contains a repeating unit derived from anunsaturated monomer having an anion group selected from the groupconsisting of a carboxyl group, a sulfonic acid group, and a phosphoricacid group, and further contains at least one of a repeating unitderived from an unsaturated monomer having a tertiary amino group and arepeating unit derived from an unsaturated monomer having a quaternaryammonium group.

[5] The core-shell type polymer particle according to any one of [1] to[4], wherein a mass ratio of the amphoteric polymer (A) to thehydrophobic polymer (B) [(A)/(B)] is 1/10 to 10/1.

[6] The core-shell type polymer particle according to any one of [1] to[5], wherein a glass transition temperature of the hydrophobic polymer(B) is −70° C. or higher and 105° C. or lower.

[7] The core-shell type polymer particle according to any one of [1] to[6], wherein the hydrophobic polymer (B) contains a structural unitderived from a hydrophobic unsaturated monomer (b), and the hydrophobicunsaturated monomer (b) contains an alkyl (meth)acrylate having ahydrocarbon chain having 1 to 45 carbon atoms.

[8] An aqueous polymer emulsion comprising the core-shell type polymerparticle according to any one of [1] to [7] dispersed in water.

[9] The aqueous polymer emulsion according to [8], wherein an averageparticle diameter of the core-shell type polymer particle dispersed inthe aqueous polymer emulsion is 10 nm to 10 μm.

[10] A hair cosmetic composition comprising the aqueous polymer emulsionaccording to [8] or [9] blended therein.

Effect of the Invention

The core-shell type polymer particle, the aqueous polymer emulsion, andthe hair cosmetic composition of the present invention sufficientlysecure water solubility of an emulsion, also have hardness, suppleness,and humidity resistance, and are capable of forming a film which iseasily washed and removed. In particular, the core-shell type polymerparticle and the aqueous polymer emulsion of the present invention areexcellent in adhesion to the hair and capable of giving favorablesetting effect and texture, and therefore, they are especially suitableas a hair cosmetic, such as hair spray, mousse, setting lotion, gel,spray, etc.

DESCRIPTION OF EMBODIMENTS <Shell Part in Core-Shell Type PolymerParticle>

The shell part in the core-shell type polymer particle of the presentinvention is composed of an amphoteric polymer (A) having both a cationand an anion within the polymer. In view of the fact that the polymerhas an anion therein, a setting power and a holding power can berevealed. In addition, in view of the fact that the polymer has a cationtherein, an affinity with the hair can be improved.

In view of the fact that the amphoteric polymer (A) in the core-shelltype polymer particle of the present invention has both a cation and ananion within the polymer, it is possible to make the affinity with thehair favorable with sufficiently having a setting power and a holdingpower.

In view of the fact that the core-shell type polymer particle of thepresent invention has the amphoteric polymer (A) in the shell part, thecharacteristics of the amphoteric polymer (A) can be exhibited directlyagainst the hair.

Examples of the amphoteric polymer (A) include polymers composed of, asan essential component, an unsaturated monomer containing a betainestructural group, such as a carboxybetaine group, a sulfobetaine groupand a phosphobetaine group; polymers composed of, as an essentialcomponent, an unsaturated monomer having an amine oxide group; polymerscomposed of, as essential components, an unsaturated monomer having ananion group, such as a carboxyl group, a sulfonic acid group and aphosphoric acid group, and at least one of an unsaturated monomer havinga group having a quaternary ammonium salt (hereinafter also referred toas a quaternary ammonium group) and an unsaturated monomer having atertiary amino group; and the like.

Specific examples of the polymer composed of, as an essential component,an unsaturated monomer having a betaine structural group includemethacrylic carboxybetaine polymers that are a monohaloacetate-modifiedproduct of a dimethylaminoethyl methacrylate/alkyl methacrylatecopolymer, such as YUKAFORMER 205S, YUKAFORMER SM, AMPHOSET, YUKAFORMER301, YUKAFORMER 104D, YUKAFORMER 202, YUKAFORMER 510, YUKAFORMER FH,YUKAFORMER 204WL, and YUKAFORMER 204WL-2 (all of which are manufacturedby Mitsubishi Chemical Corporation); and the like. These polymers aredisclosed in, for example, JP-A-S51-9732, JP-A-S55-104209,JP-A-S61-258804, JP-A-7-285832, and the like.

The polymer composed of, as an essential component, an unsaturatedmonomer having an amine oxide group (resin containing amine oxide group)is a polymer having, as a constituent component, a fatty acid acrylatehaving 1 to 24 carbon atoms, an ethylamine oxide methacrylate, and atleast one of acrylic acid and methacrylic acid and contains an amineoxide group as a structural unit. Specific examples thereof includeDIAFORMER Z-711, DIAFORMER Z-712, DIAFORMER Z-631, DIAFORMER Z-632,DIAFORMER Z-732, DIAFORMER Z-651, DIAFORMER Z-731, and DIAFORMER Z-772(all of which are manufactured by Mitsubishi Chemical Corporation), andthe like.

Specific examples of the polymer composed of, as essential components,an unsaturated monomer having an anion group, such as a carboxyl group,a sulfonic acid group and a phosphoric acid group., and at least one ofan unsaturated monomer having a quaternary ammonium group and anunsaturated monomer having a tertiary amino group include polymerscomposed of, as essential components, an unsaturated monomer having acarboxyl group and an unsaturated monomer having a tertiary amino group,that is a hydroxypropyl acrylate/butylaminoethyl methacrylate/octylamideacrylate copolymer, such as UNFOAMER 28-4910, UNFOAMER LV-71, andUNFOAMER LV-47 (all of which are manufactured by Akzo Nobel N. V.).;polymers composed of, as essential components, an unsaturated monomerhaving a carboxyl group and an unsaturated monomer having a quaternaryammonium group, that is a diallyldimethylammonium chloride/acrylic acidcopolymer, such as MERQUAT 295 (manufactured by Lubrizol Corporation),or a diallyldimethylammonium chloride/acrylic acid/acrylamide copolymer,such as MERQUAT PLUS 3330 (manufactured by Lubrizol Corporation); andthe like.

From the viewpoint of improving the affinity with the hair, therebyenabling the hairdressing effect to be improved especially at hightemperature and high humidity, it is preferred that the amphotericpolymer (A) contains a repeating unit derived from an unsaturatedmonomer having a betaine structural group.

In addition, from the viewpoint of not only improving the affinity withthe hair but also enabling the stimulativeness to the skin to be morelowered, it is preferred that the amphoteric polymer (A) contains arepeating unit derived from an unsaturated monomer having an amine oxidegroup.

In addition, from the viewpoints that a natural finish can be achievedwithout causing stickiness, and the moisture retention can be improved,it is preferred that the amphoteric polymer (A) contains a repeatingunit derived from an unsaturated monomer having an anion group selectedfrom the group consisting of a carboxyl group, a sulfonic acid group,and a phosphoric acid group and at least one of a repeating unit derivedfrom an unsaturated monomer having a quaternary ammonium group and arepeating unit derived from an unsaturated monomer having a tertiaryamino group.

<Core Part in Core-Shell Type Polymer Particle>

The core part in the core-shell type polymer particle of the presentinvention is composed of a hydrophobic polymer (B). It is preferred thata glass transition temperature of the hydrophobic polymer (B) is −70° C.or higher and 105° C. or lower. In this case, the film formability canbe improved. Furthermore, in this case, the suppleness of the film canbe improved, and the generation of flaking can be more prevented fromoccurring. From the viewpoint of improving the strength of the film, thehydrophobic polymer (B) may be crosslinked. The glass transitiontemperature of the hydrophobic polymer (B) is determined by a method asdescribed later in the Examples.

It is preferred that the hydrophobic polymer (B) contains a structuralunit derived from a hydrophobic unsaturated monomer (b). It is preferredthat the hydrophobic unsaturated monomer (b) has a hydrocarbon chainpreferably having 1 to 45 carbon atoms, and more preferably 1 to 24carbon atoms. The hydrocarbon chain may be either linear or branched. Inaddition, a hydrocarbon group having a monocyclic or polycyclicaliphatic ring or aromatic ring may also be contained. In addition, ahydrocarbon group having, as a substituent, a linear or branched alkylgroup may be further contained in the ring.

Specifically, examples of the hydrophobic unsaturated monomer (b)include methyl (meth)acrylate, ethyl (meth)acrylate, 3-methoxyethyl(meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl(meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate,hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,lauryl (meth)acrylate,stearyl (meth)acrylate, 2-phenylethyl (meth)acrylate, benzyl(meth)acrylate, tetradecyl (meth)acrylate, diethylaminoethyl(meth)acrylate, diisopropylaminoethyl (meth)acrylate, and the like.Incidentally, in the present specification, the “(meth)acrylate”expresses at least one of “acrylate” and “methacrylate”.

It is preferable that the hydrophobic unsaturated monomer (b) is analkyl (meth)acrylate having a hydrocarbon chain having 1 to 45 carbonatoms. In the foregoing range of the carbon number, in the case wherethe glass transition temperature (Tg) of the polymer after thepolymerization is low, a soft film can be formed, whereas in the case ofusing a monomer having a high Tg, a hard film can be formed. By using analkyl (meth)acrylate having a hydrocarbon chain having the foregoingcarbon number range, it is possible to form a film in conformity with adesired styling power.

In addition, a functional group-containing monomer (c) may becopolymerized with the above-described hydrophobic unsaturated monomer(b). Examples of the monomer (c) containing functional group include amonomer having two or more vinyl groups in a molecular structurethereof, a monomer containing a glycidyl group, a monomer containing anallyl group, a monomer containing a hydrolyzable silyl group, a monomercontaining an acetoacetyl group, a monomer containing a hydroxyl group,a monomer containing a carboxyl group, and the like.

Of these, it is preferred that a monomer having two or more vinyl groupsin a molecular structure thereof or a monomer containing a hydrolyzablesilyl group is copolymerized from the standpoint that the waterwashability is improved without deteriorating the hairdressingproperties.

Examples of the monomer having two or more vinyl groups in a molecularstructure thereof include divinylbenzene, diallyl phthalate, triallylcyanurate, triallyl isocyanurate, ethylene glycol di(meth)acrylate,1,2-propylene glycol di(meth)acrylate, 1,3-propylene glycoldi(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropanetri(meth)methacrylate, allyl (meth)acrylate, and the like.

Of these, ethylene glycol di(meth)acrylate, 1,2-propylene glycoldi(meth)acrylate, 1,3-propylene glycol di(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, or trimethylolpropane tri(meth)acrylate is preferredfrom the standpoint of copolymerizability with the (meth)arylate-basedmonomer.

Examples of the monomer containing a glycidyl group include glycidyl(meth)acrylate, glycidyl (meth)allyl ether, 3,4-epoxycyclohexyl(meth)acrylate, and the like.

Examples of the monomer containing an allyl group include a monomerhaving two or more allyl groups, such as triallyloxyethylene, diallylmaleate, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane,trimethylolpropane diallyl ether, pentaerythritol triallyl ether, etc.,allyl glycidyl ether, allyl acetate, and the like.

Examples of the monomer containing a hydrolyzable silyl group includemonomers containing vinyl-based silyl group, such asvinyltrimethoxysilane, vinyltriethoxysilane,vinyltris(β-methoxyethoxy)silane, vinylmethyldimethoxysilane, etc.; andmonomers containing (meth)acryloxy-based silyl group, such asγ-(meth)acryloxypropyltrimethoxysilane,γ-(meth)acryloxypropylmethyldimethoxysilane,γ-(meth)acryloxypropyltriethoxysilane,γ-(meth)acryloxypropylmethyldiethoxysilane, etc. Of these, monomerscontaining (meth)acryloxy-based silyl group are preferred from thestandpoint of excellent copolymerizability with the hydrophobicunsaturated monomer (b). Incidentally, in the present specification, the“(meth)acryloxy” expresses at least one of “acryloxy” and“methacryloxy”.

Examples of the monomer containing an acetoacetyl group include vinylacetoacetate, allyl acetoacetate, allyl di acetoacetate,acetoacetoxyethyl (meth)acrylate, acetoacetoxyethyl crotonate,acetoacetoxypropyl (meth)acrylate, acetoacetoxypropyl crotonate,2-cyanoacetoacetoxyethyl (meth)acrylate, and the like.

Examples of the monomer containing a hydroxyl group include(meth)acrylates, such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.; and the like. Ofthese, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate ispreferred from the viewpoints of protective colloid action at the timeof emulsion polymerization and water washability.

Examples of the monomer containing a carboxyl group include(meth)acrylic acid, an acrylic acid dimer, crotonic acid, maleic acid,maleic anhydride, fumaric acid, citraconic acid, glutaconic acid,itaconic acid, acrylamide N-glycolic acid, cinnamic acid, and the like.Of these, acrylic acid or methacrylic acid is preferred from theviewpoints of protective colloid action at the time of emulsionpolymerization and water washability.

A content proportion of the monomer (c) containing the functional groupis preferably 10% by weight or less, more preferably 5% by weight orless, and still more preferably 3% by weight or less relative to thewhole of the monomer components. By regulating the content to thisrange, the matter that the hydrophobic polymer (B) becomes excessivelyhard is inhibited, a sufficient adhesiveness is exhibited, and thehairdressing properties can be more improved. In addition, from theviewpoint of sufficiently obtaining an improving effect of waterwashability, the content proportion of the monomer (c) containing thefunctional group is preferably 0.01% by weight or more, more preferably0.05% by weight or more, and still more preferably 0.1% by weight ormore relative to the whole of the monomer components.

In addition, in the case where the monomer (c) containing the functionalgroup is a monomer having two or more vinyl groups in a molecularstructure thereof, the content thereof is preferably 0.01 to 5% byweight, more preferably 0.05 to 3% by weight, and still more preferably0.1 to 1% by weight relative to the whole of the monomer components.

In addition, besides, in a range where the effects of the presentinvention are not impaired, a small amount of styrene or a styrene-basedmonomer, such as α-methylstyrene, etc., or a vinyl ester-based monomer,such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate,vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprylate,vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, vinyl2-ethylhexanoate, etc., may be used.

In the aqueous polymer emulsion of the present invention, in addition tothe above-described monomer components, other component can be furtherused, if desired. Such other component may be properly selectedaccording to the purpose, and examples thereof include a polymerizationinitiator, a polymerization modifier, a co-emulsifier, a plasticizer,and the like.

As the polymerization initiator, those which can be used for usualemulsion polymerization can be used. Examples thereof include aninorganic peroxide, such as potassium persulfate, sodium persulfate,ammonium persulfate, etc.; an organic peroxide; an azo-based initiator;a redox polymerization initiator composed of a peroxide, such ashydrogen peroxide, butyl peroxide, etc., in combination with a reducingagent, such as acidic sodium sulfite, L-ascorbic acid, etc.; and thelike. These can be used alone or in combination of two or more thereof.Of these, ammonium persulfate or potassium persulfate is preferred fromthe standpoint that the polymerization is easy.

The polymerization modifier can be properly selected among those whichare known. Examples of such a polymerization modifier include a chaintransfer agent, a buffer, and the like.

Examples of the chain transfer agent include alcohols, such as methanol,ethanol, propanol, butanol, etc.; aldehydes, such as acetaldehyde,propionaldehyde, n-butylaldehyde, furfural, benzaldehyde, etc.;mercaptans, such as dodecyl mercaptan, lauryl mercaptan, normalmercaptan, thioglycolic acid, octyl thioglycolate, thioglycerol, etc.;and the like. These can be used alone or in combination of two or morethereof. The use of the chain transfer agent is effective from thestandpoint that the polymerization is stably achieved, and it ispreferred to use the chain transfer agent for the purpose of regulatinga degree of polymerization of the hydrophobic polymer (B).

As the co-emulsifier, any materials which are known to be usable for theemulsion polymerization by a person skilled in the art can be used.Accordingly, the co-emulsifier can be properly selected among knownmaterials, for example, anionic, cationic, and nonionic surfactants,water-soluble polymers having a protective colloid ability other thanthe amphoteric polymer (A), water-soluble oligomers, and the like.

Examples of the surfactant include anionic surfactants, such as sodiumlauryl sulfate, sodium dodecyl benzenesulfonate, etc.; and nonionicsurfactants, such as those having a Pluronic type structure, thosehaving a polyoxyethylene type structure, etc. Of these surfactants,among ionic surfactants, especially anionic surfactants, anionicsurfactants, such as sodium stearoylmethyl taurate, sodium stearoylglutamate, sodium stearoyl lactate, etc., are preferred. In addition, asthe surfactant, a reactive surfactant having a radical polymerizableunsaturated bond in a structure thereof can also be used. These can beused alone or in combination of two or more thereof.

The use of the surfactant has an effect for smoothly advancing or easilycontrolling the emulsion polymerization (effect as an emulsifier), orsuppressing the generation of coarse particles or the generation of ablock-like material during the polymerization. However, when a largeamount of such a surfactant is used as an emulsifier, there is apossibility that the shell is separated from the core. For that reason,in the case of using the surfactant, it is preferred that the use amountthereof is an auxiliary amount against the amphoteric polymer (A),namely, the use amount is made small as far as possible.

The core part of the core-shell type polymer particle of the presentinvention can be selected from the hydrophobic polymer (B). According tothis, at the time when a hair cosmetic using the core-shell type polymerparticle of the present invention is used for the hair, the touchfeeling or softness or the like can be regulated.

<Core-Shell Type Polymer Particle>

The core-shell type polymer particle of the present invention has theabove-described shell part and the above-described core part. Accordingto this, it is possible to provide the softness of touch with realizingthe hardness necessary for a hair cosmetic, especially a hairdressingagent.

As an analysis method of the core-shell structure of the core-shell typepolymer particle of the present invention, for example, TEM(transmission electron microscope) can be used. The observation can beperformed by applying the aqueous polymer emulsion of the presentinvention on a carbon support film and then drying. It is preferred todye the core-shell type polymer particle with osmium tetroxide,ruthenium tetroxide, chlorosulfonic acid/uranyl acetate, silver sulfide,or the like. In this case, the contrast can be made large.

From the viewpoints of improving the suppleness, the softness, and thehumidity resistance at higher levels and more preventing the generationof flaking from occurring, a mass ratio of the amphoteric polymer (A) tothe hydrophobic polymer (B) [(A)/(B)] in the core-shell type polymerparticle is preferably 1/10 to 10/1. In addition, in this case, there isa tendency that the polymerization is easy to be stably advanced; thereis a tendency that coarse particles or block-like polymer pieces arehardly generated during the polymerization; and there is a tendency thatthe storage stability of the aqueous polymer emulsion is improved.Furthermore, there is a tendency that the hair washability is improved.

The mass ratio of the amphoteric polymer (A) to the hydrophobic polymer(B) [(A)/(B)] is more preferably from 1/5 to 5/1. By completing thepolymerization within this range, an effect for making the particlesuniform is exhibited, and it becomes possible to obtain an emulsionsolution with excellent storage stability. In addition, the emulsion isexcellent in transparency or uniformity at the time of film formation,and even in the case of applying to the hair, it becomes possible torealize styling having both flexibility and suppleness. In addition, itis possible to much more prevent the generation of flaking fromoccurring.

<Aqueous Polymer Emulsion>

The aqueous polymer emulsion of the present invention is one in whichthe core-shell type polymer of the present invention is dispersed inwater. From the viewpoints of stability of the emulsion and smoothnessand transparency of the formed film, an average particle diameter of thecore-shell type polymer particle in the aqueous polymer emulsion ispreferably from 10 nm to 10 more preferably from 10 to 500 nm, and stillmore preferably from 10 to 300 nm.

As shown in the Examples as described later, the core-shell type polymerparticle of the present invention is produced as the above-describedaqueous polymer emulsion dispersed in water and used. By drying thisaqueous polymer emulsion by means of freeze drying or the like, apowdered core-shell type polymer particle can also be obtained. In thiscase, since the volume or weight at the time of transportation can bemade small, the transportation becomes easy, so that it can be devisedto reduce the transportation costs. By dispersing the powderedcore-shell type polymer particle, the aqueous polymer emulsion isobtained.

<Hair Cosmetic Composition>

The hair cosmetic composition of the present invention is one includingthe above- described aqueous polymer emulsion blended therein. In a haircosmetic composition, in addition to the aqueous polymer emulsion,components which are used for usual cosmetics may be properly blendedwith a range where the effects of the present invention are notimpaired.

As such a component, for example, glycerides, such as camellia oil,castor oil, cacao oil, mink oil, avocado oil, jojoba oil, macadamia nutoil, olive oil, etc.; waxes, such as beeswax, lanolin, etc.;hydrocarbons, such as liquid paraffin, solid paraffin, isoparaffin,squalane, etc.; linear or branched higher alcohols, such as cetylalcohol, oleyl alcohol, stearyl alcohol, isostearyl alcohol, laurylalcohol, 2-octyl decanol, etc.; polyhydric alcohols, such as ethyleneglycol, polyethylene glycol, propylene glycol, polypropylene glycol,glycerin, sorbitol, etc.; ethylene oxide and/or propylene oxide adductsof a higher alcohol, such as polyoxyethylene lauryl ether,polyoxypropylene cetyl alcohol, polyoxyethylene polyoxypropylene stearylether, etc.; esters, such as isopropyl myristate, octyldodecylmyristate, hexyl laurate, cetyl lactate, etc.; amides, such as oleicacid diethanolamide, lauric acid diethanolamide, etc.; siliconederivatives, such as dimethylpolysiloxane, methylphenyl polysiloxane,polyether-modified silicone, amino-modified silicone, etc.; cationicsurfactants, such as stearyltrimethylammonium chloride, distearyldimethylammonium chloride, lauryltrimethylammonium chloride,etc.; anionic surfactants, such as polyoxyethylene lauryl ether sulfate,polyoxyethylene lauryl sulfosuccinate, etc.; amphoteric surfactants,such as lauryl hydroxysulfobetaine, lauryl dimethylcarboxybetaine, etc.;protein derivatives or amino acid derivatives, such as a collagenhydrolyzate, a keratin hydrolyzate, a polyamino acid, etc.; UVabsorbers, such as plant extracts, crude drugs, vitamins, oxybenzene,etc.; chelating agents, such as EDTA-Na, etc.; antiseptics, such asparaben, etc.; antioxidants; coloring matters; pigments; flavors; and soon may be properly blended within a range where the effects of thepresent invention are not impaired.

The hair cosmetic composition of the present invention is notparticularly limited with respect to an application thereof, and forexample, it may be used as a hairdressing agent, a setting agent, ashampoo, a rinse, a conditioner, or a hair treatment. Of these, ahairdressing agent or a setting agent is preferred. This is because whenthe amphoteric polymer (A) is used in the shell part of the core-shelltype polymer particle of the present invention, a setting power or aholding power is revealed. In the case where the polymer in the shellpart is a cationic polymer, there are a lot of cationic polymers whichhave a high affinity with the hair but do not harm a feeling of thehair. Therefore, while such a cationic polymer is suitable as a coloringagent, a rinse, a conditioner, or a hair treatment, in general, it ishardly used as a hairdressing agent.

The hair cosmetic composition of the present invention is notparticularly limited with respect to a form of use, and it can be, forexample, used as an aerosol hair spray, a pump type hair spray, a foamtype hair spray, a hair mist, a setting lotion, a hair gel, a haircream, a hair oil, or the like.

The hair cosmetic can also be formed in an aerosol agent type accordingto the usual way by using, as a propellant, a chlorofluoroalkane, suchas trichloromonofluoromethane, dichlorodifluoromethane, etc.; aliquefied petroleum gas composed of an alkane; dimethyl ether; acompressed gas, such as a carbon dioxide gas and a nitrogen gas; or thelike, or a mixed gas thereof. Besides the hair cosmetic, the compositionof the present invention can also be used for skin care, sun care,makeup, or the like.

EXAMPLES

Although the present invention is more specifically described belowbased on the Examples, it should be construed that the present inventionis by no means limited by the following Examples.

Example 1

Example of an aqueous polymer emulsion in which a core-shell typepolymer particle having a core part composed of a hydrophobic polymerand a shell part covering this core part and composed of an amphotericpolymer is dispersed in water is described. The aqueous polymer emulsionof the present Example was produced in the following manner.

First of all, YUKAFORMER AMPHOSET, manufactured by Mitsubishi ChemicalCorporation was prepared as an amphoteric polymer. This is hereunderreferred to as “Amphoteric Polymer I”. Subsequently, in a reactorequipped with a reflux condenser, a dropping pump, a thermometer, anitrogen gas introducing pipe, and a stirring device, 22.5 g ofAmphoteric Polymer I and 70 g of water were added to prepare an aqueousphase, and this aqueous phase was heated to 60° C. in a nitrogenatmosphere.

Subsequently, 0.64 g of a 70% by mass t-butyl hydroperoxide aqueoussolution (initiator) was diluted with 5.8 g of water to prepare aninitiator diluted solution, and this initiator diluted solution wasadded to the aqueous phase. Thereafter, 0.23 g of ascorbic acid wasdiluted with water to prepare a 1% by mass ascorbic acid aqueoussolution, and this ascorbic acid aqueous solution was added to theaqueous phase, followed by thoroughly stirring.

In addition, 22.5 g of Amphoteric Polymer I and 45 g of butyl acrylate(BA) were mixed to prepare a uniform oil phase. To this oil phase, 70 gof water was added, and the contents were stirred with a homomixer at arotation speed of 3,000 rpm for 5 minutes, to obtain a pre-emulsion.

Subsequently, the pre-emulsion was dropped in the aqueous phase at atemperature of 60° C. within the reactor over 1 hour by the droppingpump. Subsequently, the temperature within the reactor was elevated to65° C., and the contents were polymerized for 3 hours, to obtain anaqueous polymer emulsion.

This aqueous polymer emulsion was one in which the core-shell typepolymer particle having a core part composed of polybutyl acrylate (BA)and a shell part covering this core part and composed of AmphotericPolymer I was dispersed in water.

The kind and blending proportion of the amphoteric polymer forming theshell part in the core-shell type polymer particle in the presentExample are shown in Table 1 as described later. In addition, the kindand blending proportion of the monomer [(meth)acrylic acid ester]constituting the hydrophobic polymer forming the core part in thecore-shell type polymer particle are shown in Table 1 as describedlater.

Furthermore, a mass ratio of the amphoteric polymer (A) forming theshell part to the hydrophobic polymer (B) forming the core part[(A)/(B)] is shown in Table 1 as described later. In this connection, aviscosity of the aqueous polymer emulsion at 25° C. was 12 mPa·s.

Subsequently, an average particle diameter of the core-shell typepolymer particle in the aqueous polymer emulsion was measured. Theresults are shown in Table 1 as described later. The average particlediameter was a particle diameter at a volume integrated value of 50% inthe particle size distribution determined by the laser diffraction andscattering method and measured with a laser diffraction particle sizedistribution analyzer (Nanotrac 150, manufactured by Nikkiso Co., Ltd.).

In addition, a glass transition temperature Tg (° C.) of the polymer(acrylic resin) forming the core part of the core-shell type polymerparticle was calculated. The Tg of the polymer of the core part is atheoretical calculation value as determined according to the FOXequation represented by the following equation (1).

1/Tg=W1/Tg1+W2/Tg2+ . . . + Wn/Tgn  (1)

In the formula (1), Tg is a glass transition temperature of the polymer(acrylic resin) forming the core part; W1, W2, . . . , Wn are each aweight fraction of each of the monomers constituting the polymer; andTg1, Tg2, . . . , Tg n are each a glass transition temperature of eachof homopolymers of the monomers.

As the glass transition temperatures of the homopolymers, knownliterature values can adopted. Specifically, these glass transitiontemperatures are described in, for example, Acrylic Ester Catalogue ofMitsubishi Rayon Co., Ltd. (1977 Version); Kyozo Kitaoka, “Shin KobunshiBunko 7, Guide to Synthetic Resin, for Coating Material”, KobunshiKankokai, published in 1997, pp.168-169; and so on.

Example 2

An aqueous polymer emulsion was prepared in the same manner as inExample 1, except that in the preparation of the oil phase in Example 1,45 g of butyl acrylate (BA) used was changed to 8.8 g of methylmethacrylate (MMA), 20.5 g of butyl acrylate (BA), and 15.7 g ofisobutyl methacrylate (i-BMA).

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate/isobutyl methacrylate), and ashell part composed of Amphoteric Polymer I which is same as in Example1 was dispersed in water. The composition and physical properties, andso on of the core-shell type polymer particle in the aqueous polymeremulsion of the present Example are shown in Table 1 as described laterin the same manner as in Example 1.

Example 3

An aqueous polymer emulsion was prepared in the same manner as inExample 1, except that in the preparation of the oil phase in Example 1,45 g of butyl acrylate (BA) used was changed to 28.4 g of methylmethacrylate (MMA), 12.1 g of butyl acrylate (BA), and 4.5 g of stearylmethacrylate (SMA).

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate/stearyl methacrylate), and ashell part composed of Amphoteric Polymer I which is same as in Example1 was dispersed in water. The composition and physical properties, andso on of the core-shell type polymer particle in the aqueous polymeremulsion of the present Example are shown in Table 1 as described laterin the same manner as in Example 1.

Example 4

To prepare an aqueous phase, 22.5 g of Amphoteric Polymer I and 70 g ofwater used for the preparation of the aqueous phase in Example 1 werechanged to 37.5 g of Amphoteric Polymer II (YUKAFORMER 510, manufacturedby Mitsubishi Chemical Corporation) and 60 g of water, respectively.

In addition, in the preparation of the oil phase in Example 1, 22.5 g ofAmphoteric Polymer I used was changed to 37.5 g of Amphoteric PolymerII, and 45 g of butyl acrylate (BA) used was changed to 31.5 g of methylmethacrylate (MMA) and 13.5 g of 2-ethylhexyl acrylate (2EHA), toprepare an oil phase. Furthermore, the amount of water to be added tothe oil phase was changed to 60 g, to prepare a pre-emulsion. Besides,the same procedures as in Example 1 were followed to prepare an aqueouspolymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/2-ethylhexyl acrylate) and a shell partcomposed of Amphoteric Polymer II was dispersed in water. Thecomposition and physical properties, and so on of the core-shell typepolymer particle in the aqueous polymer emulsion of the present Exampleare shown in Table 1 as described later in the same manner as in Example1.

Example 5

In the preparation of the aqueous phase in Example 1, 22.5 g ofAmphoteric Polymer I and 70 g of water used were changed to 132.35 g ofAmphoteric Polymer III (YUKAFORMER 204WL-2, manufactured by MitsubishiChemical Corporation) and 5.0 g of water, respectively, to prepare anaqueous phase.

In addition, in the preparation of the oil phase in Example 1, 22.5 g ofAmphoteric Polymer I used was changed to 132.35 g of Amphoteric PolymerIII, and 45 g of butyl acrylate (BA) used was changed to 31.5 g ofmethyl methacrylate (MMA) and 13.5 g of butyl acrylate (BA), to preparean oil phase. Furthermore, the amount of water to be added to the oilphase was changed to 5.0 g, to prepare a pre-emulsion. Besides, the sameprocedures as in Example 1 were followed to prepare an aqueous polymeremulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate) and a shell part composed ofAmphoteric Polymer III was dispersed in water. The composition andphysical properties, and so on of the core-shell type polymer particlein the aqueous polymer emulsion of the present Example are shown inTable 1 as described later in the same manner as in Example 1.

Example 6

In the preparation of the aqueous phase in Example 1, 22.5 g ofAmphoteric Polymer I and 70 g of water used were changed to 26.5 g ofAmphoteric Polymer 111 (YUKAFORMER 204WL-2, manufactured by MitsubishiChemical Corporation) and 43.2 g of water, respectively, to prepare anaqueous phase.

In addition, in the preparation of the oil phase in Example 1, 22.5 g ofAmphoteric Polymer I used was changed to 26.5 g of Amphoteric PolymerIII, and 45 g of butyl acrylate (BA) used was changed to 31.5 g ofmethyl methacrylate (MMA) and 13.5 g of butyl acrylate (BA), to preparean oil phase. Furthermore, the amount of water to be added to the oilphase was changed to 43.2 g, to prepare a pre-emulsion. Besides, thesame procedures as in Example 1 were followed to prepare an aqueouspolymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate) and a shell part composed ofAmphoteric Polymer III was dispersed in water. The composition andphysical properties, and so on of the core-shell type polymer particlein the aqueous polymer emulsion of the present Example are shown inTable 1 as described later in the same manner as in Example 1.

Example 7

In the preparation of the aqueous phase in Example 1, 22.5 g ofAmphoteric Polymer I and 70 g of water used were changed to 37.5 g ofAmphoteric Polymer IV (DIAFORMER Z-632, manufactured by MitsubishiChemical Corporation) and 60 g of water, respectively, to prepare anaqueous phase.

In addition, in the preparation of the oil phase in Example 1, 22.5 g ofAmphoteric Polymer I used was changed to 37.5 g of Amphoteric PolymerIV, and 45 g of butyl acrylate (BA) used was changed to 31.5 g of methylmethacrylate (MMA) and 13.5 g of butyl acrylate (BA), to prepare an oilphase. Furthermore, the amount of water to be added to the oil phase waschanged to 60 g, to prepare a pre-emulsion.

Besides, the same procedures as in Example 1 were followed to prepare anaqueous polymer emulsion. The aqueous polymer emulsion of the presentExample was one in which the core-shell type polymer particle having acore part composed of poly(methyl methacrylate/butyl acrylate) and ashell part composed of Amphoteric Polymer IV was dispersed in water. Thecomposition and physical properties, and so on of the core-shell typepolymer particle in the aqueous polymer emulsion of the present Exampleare shown in Table 1 as described later in the same manner as in Example1.

Example 8

In the preparation of the oil phase in Example 1, 45 g of butyl acrylate(BA) used was changed to 6.75 g of methyl methacrylate (MMA), 15.75 g ofbutyl acrylate (BA), and 22.5 g of stearyl methacrylate (SMA), toprepare an oil phase. Besides, the same procedures as in Example 1 werefollowed to prepare an aqueous polymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate/stearyl methacrylate) and ashell part composed of Amphoteric Polymer I was dispersed in water. Thecomposition and physical properties, and so on of the core-shell typepolymer particle in the aqueous polymer emulsion of the present Exampleare shown in Table 1 as described later in the same manner as in Example1.

Example 9

In the preparation of the oil phase in Example 1, 45 g of butyl acrylate(BA) used was changed to 45 g of methyl methacrylate (MMA), to preparean oil phase. Besides, the same procedures as in Example 1 were followedto prepare an aqueous polymer emulsion. The aqueous polymer emulsion ofthe present Example was one in which the core-shell type polymerparticle having a core part composed of polymethyl methacrylate and ashell part composed of Amphoteric Polymer I was dispersed in water. Thecomposition and physical properties, and so on of the core-shell typepolymer particle in the aqueous polymer emulsion of the present Exampleare shown in Table 1 as described later in the same manner as in Example1.

Example 10

First of all, a polymer composed of, as essential components, both of anunsaturated monomer containing a carboxyl group and an unsaturatedmonomer containing a tertiary amino group, which is a hydroxypropylacrylate/butylaminoethyl methacrylate/octylamide acrylate copolymer(UNFOAMER 28-4910, manufactured by National Starch), was dissolved in anethanol solution.

Subsequently, 90% of 100% of an acid equivalent of the polymer in theresulting solution was neutralized with 2-amino-2-methyl-1-propanol andregulated such that a polymer solid content of UNFOAMER 28-4910 was 30%by mass, to obtain Amphoteric Polymer V.

Subsequently, in the preparation of the aqueous phase in Example 1, 22.5g of Amphoteric Polymer I and 70 g of water used were changed to 37.5 gof Amphoteric Polymer V and 60 g of water, respectively, to prepare anaqueous phase. In addition, in the preparation of the oil phase inExample 1, 22.5 g of Amphoteric Polymer I used was changed to 37.5 g ofAmphoteric Polymer V, and 45 g of butyl acrylate (BA) used was changedto 31.5 g of methyl methacrylate (MMA) and 13.5 g of butyl acrylate(BA), to prepare an oil phase. Furthermore, the amount of water to beadded to the oil phase was changed to 60 g, to prepare a pre-emulsion.Besides, the same procedures as in Example 1 were followed to prepare anaqueous polymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate) and a shell part composed ofAmphoteric Polymer V was dispersed in water. The composition andphysical properties, and so on of the core-shell type polymer particlein the aqueous polymer emulsion of the present Example are shown inTable 1 as described later in the same manner as in Example 1.

Example 11

In the preparation of the aqueous phase in Example 1, 22.5 g ofAmphoteric Polymer I and 70 g of water used were changed to 54 g ofAmphoteric Polymer I and 45 g of water, respectively, to prepare anaqueous phase. In addition, a solution prepared by diluting 0.06 g of70% by mass of a t-butyl hydroperoxide aqueous solution (initiator) with0.6 g of water was used as an initiator diluted solution, and this wasadded to the aqueous phase.

In addition, a solution prepared by diluting 0.02 g of ascorbic acidwith water was used as a 1% by mass ascorbic acid aqueous solution, andthis was added to the aqueous phase. In addition, in the preparation ofthe oil phase in Example 1, 22.5 g of Amphoteric Polymer I used waschanged to 54 g of Amphoteric Polymer I, and 45 g of butyl acrylate (BA)used was changed to 3.15 g of methyl methacrylate (MMA) and 1.35 g ofbutyl acrylate (BA), to prepare an oil phase. Furthermore, the amount ofwater to be added to the oil phase was changed to 45 g, to prepare apre-emulsion. Besides, the same procedures as in Example 1 were followedto prepare an aqueous polymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate) and a shell part composed ofAmphoteric Polymer I was dispersed in water. The composition andphysical properties, and so on of the core-shell type polymer particlein the aqueous polymer emulsion of the present Example are shown inTable 1 as described later in the same manner as in Example 1.

Example 12

In the preparation of the aqueous phase in Example 1, 22.5 g ofAmphoteric Polymer I and 70 g of water used were changed to 7.5 g ofAmphoteric Polymer I and 60 g of water, respectively, to prepare anaqueous phase. In addition, in the preparation of the oil phase inExample 1, 22.5 g of Amphoteric Polymer I used was changed to 7.5 g ofAmphoteric Polymer I, and 45 g of butyl acrylate (BA) used was changedto 31.5 g of methyl methacrylate (MMA) and 13.5 g of butyl acrylate(BA), to prepare an oil phase. Furthermore, the amount of water to beadded to the oil phase was changed to 60 g, to prepare a pre-emulsion.Besides, the same procedures as in Example 1 were followed to prepare anaqueous polymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate) and a shell part composed ofAmphoteric Polymer I was dispersed in water. The composition andphysical properties, and so on of the core-shell type polymer particlein the aqueous polymer emulsion of the present Example are shown inTable 1 as described later in the same manner as in Example 1.

Comparative Example 1

In the preparation of the aqueous phase in Example 1, 22.5 g ofAmphoteric Polymer I and 70 g of water used was changed to a 30% by masssolution prepared by dissolving 11.25 g of polyvinylpyrrolidone (PVP)(Luviskol K90 Powder, manufactured by BASF SE) in 26.25 g of ethanol and60 g of water, respectively, to prepare an aqueous phase.

In addition, in the preparation of the oil phase in Example 1, 22.5 g ofAmphoteric Polymer 1 used was changed to a 30% by mass solution preparedby dissolving 11.25 g of PVP in 26.25 g of ethanol, and 45 g of butylacrylate (BA) used was changed to 31.5 g of methyl methacrylate (MMA)and 13.5 g of butyl acrylate (BA), to prepare an oil phase. Furthermore,the amount of water to be added to the oil phase was changed to 60 g, toprepare a pre- emulsion. Besides, the same procedures as in Example 1were followed to prepare an aqueous polymer emulsion.

The aqueous polymer emulsion of the present Example was one in which thecore-shell type polymer particle having a core part composed ofpoly(methyl methacrylate/butyl acrylate) and a shell part composed ofPVP was dispersed in water. The composition and physical properties, andso on of the core-shell type polymer particle in the aqueous polymeremulsion of the present Example are shown in Table 1 as described laterin the same manner as in Example 1.

Comparative Example 2

An amphoteric polymer “YUKAFORMER 510” (manufactured by MitsubishiChemical Corporation) was used in place of the aqueous polymer emulsionof Example 1. Namely, Comparative Example 2 is composed of theamphoteric polymer and does not have a core-shell type structure.

Experimental Examples

Using each of the aqueous polymer emulsions of Examples 1 to 12 andComparative Example 1 and the amphoteric polymer of Comparative Example2, a film was formed on the hair and evaluated for hardness, suppleness,humidity resistance, and flaking of the film and also evaluated forwashability in the following manners. The results are shown in Table 1.

“Hardness”

The hardness of the hair having a film formed thereon was evaluated byperforming the three-point bending test in conformity with JIS K7171(2008). Specifically, first of all, 0.4 g of each of the aqueous polymeremulsions of Examples 1 to 12 and Comparative Example 1 (aqueoussolutions having a solid content of 5% by mass) and the amphotericpolymer of Comparative Example 2 was applied onto a hair bundle of hairhaving a length of 15 cm and a weight of 1.3 g.

Subsequently, the hair bundle was combed with a comb and formed in aplate-like state having a width of 2 cm, which was then dried at 50° C.for 2 hours to form a film. There was thus obtained a plate-like hairhaving the film formed on a surface thereof. Subsequently, the hair wasallowed to stand for 24 hours under a condition at 23° C. and a relativehumidity of 60%. Thereafter, the plate-like hair was placed on a supporttable having a supporting point distance of 65 mm, and a central part ofthe hair was pressed by an indenter at a rate of 2 cm/sec (three-pointbending test). Then, a maximum load (bending strength) at a point oftime when the central part of the hair was bent to a depth of 2 cm wasmeasured.

The case where the maximum load is 100 g or more was evaluated as “A”;the case where the maximum load is 70 g or more and less than 100 g wasevaluated as “B”; the case where the maximum load is 50 g or more andless than 70 g was evaluated as “C”; and the case where the maximum loadis less than 50 g was evaluated as “D”.

“Suppleness”

The suppleness was evaluated by measuring a bending strength of the hairbundle after breaking the film. Specifically, the hair bundle aftermeasuring the bending strength in the above-described evaluation ofhardness was placed on a rectangular edge and pulled at a rate of about15 cm/sec with holding with a hand, thereby breaking the hair bundle.Thereafter, the three-point bending test was performed in the samemanner as in the above-described evaluation of hardness, to measure thebending strength (maximum load) of the hair bundle.

Then, the case where the load is 40 g or more was evaluated as “A”; thecase where the load is 30 g or more and less than 40 g was evaluated as“B”; the case where the load is 20 g or more and less than 30 g wasevaluated as “C”; and the case where the load is less than 20 g wasevaluated as “D”.

“Softness”

Each of the aqueous polymer emulsions of Examples 1 to 12 andComparative Example 1 (aqueous solutions having a solid content of 5% bymass) and the amphoteric polymer of Comparative Example 2 was subjectedto an actual use test. As for the solution, the softness afterapplication was evaluated by 10 expert panels.

The case where less than 2 panels perceived that after the application,the softness was not felt was evaluated as “A”; the case where 2 or moreand less than 4 panels perceived that after the application, thesoftness was not felt was evaluated as “B”; the case where 4 or more andless than 7 panels perceived that after the application, the softnesswas not felt was evaluated as “C”; and the case where 7 or more panelsperceived that after the application, the softness was not felt wasevaluated as “D”.

“Humidity Resistance”

The humidity resistance was evaluated by measuring a curl retention ofthe hair having the film formed thereon. 0.7 g of each of the aqueouspolymer emulsions of Examples 1 to 12 and Comparative Example 1 (aqueoussolutions having a solid content of 5% by mass) and the amphotericpolymer of Comparative Example 2 was applied onto a black virgin hair(length: 23 cm, weight: 2 g), a curl was immediately prepared using acurler having a curl diameter of 1.2 cm, and this was dried at 50° C.for 2 hours.

A length of this curled hair strand was measured. This length isdesignated as an initial value (L0). Subsequently, the dried hair strandwas hung on a memory-provided board and charged in a high temperatureand high humidity chamber for 3 hours at a temperature of 30° C. and arelative humidity of 90%, and a length of the hair strand was measured.This length is designated as a length (L1) after humidification. In thisconnection, when the hair strand is in a curled state, the length of thehair strand is a maximum diameter of the curl, whereas when the curl ispartially or wholly loosened, the length of the hair strand is a maximumlength from the end of the side of the root of hair (for example, alength of from the end of the side of the root of hair to the tip ofhair). Subsequently, a curl retention value was calculated according tothe following equation (2). In this connection, it is meant that thecurl retention rate is stronger, the humidity resistance is moreexcellent, and the styling holding power is more excellent as the curlretention value is closer to 100%.

Curl retention value(%)=100×(23−L1)/(23−L0)  (2)

Then, the case where the curl retention value is 85% or more wasevaluated as “A”; the case where the curl retention value is less than85% and 70% or more was evaluated as “B”; the case where the curlretention value is less than 70% and 45% or more was evaluated as “C”;and the case where the curl retention value is less than 45% wasevaluated as “D”.

“Washability”

Each of the aqueous polymer emulsions of Examples 1 to 12 andComparative Example 1 (25% by mass aqueous solutions) and the amphotericpolymer of Comparative Example 2 was applied on a glass plate using anapplicator having a coating film width of 100 μm and then dried at 50°C. for 2 hours, to form a film on the glass plate. Subsequently, thefilm was held for 24 hours under a condition at 23° C. and a relativehumidity of 60%. Thereafter, the film was dipped in warm water at 40°C., and a time until the film was completely dissolved was measured.

Then, the case where the time until dissolution is within 1 minute wasevaluated as “A”; the case where the time until dissolution is more than1 minute and within 3 minutes was evaluated as “B”; the case where thetime until dissolution is more than 3 minutes and within 5 minutes wasevaluated as “C”; and the case where even when the time exceeds 5minutes, the film is not completely dissolved was evaluated as “D”.

“Flaking”

A predetermined amount of each of the aqueous polymer emulsions ofExamples 1 to 12 and Comparative Example 1 and the amphoteric polymer ofComparative Example 2 was applied on a hair bundle of hair and thencompletely dried. Thereafter, the hair bundle was allowed to passthrough a comb, and the amount of a peeled polymer piece existent on thehair was observed with a stereoscopic microscope having a magnificationof 20 times, thereby examining the state of flaking.

Then, the case where the peeled polymer piece is not confirmed at allwas evaluated as “A”; the case where the peeled polymer piece is notsubstantially confirmed was evaluated as “B”; the case where the peeledpolymer piece is slightly confirmed was evaluated as “C”; and a verylarge amount of the peeled polymer piece is confirmed was evaluated as“D”

In this connection, in the foregoing, “A” means “very good”; “B” means“good”; “C” means “moderate”; and “D” means “bad”.

TABLE 1 Comparative Example Example 1 2 3 4 5 6 7 8 9 10 11 12 1 2Amphoteric Amphoteric Polymer I 33 33 33 33 33 92.3 14.3 polymerAmphoteric Polymer II 33 100 Amphoteric Polymer III 50 16 AmphotericPolymer IV 33 Amphoteric Polymer V 33 PVP 33 Acrylate MMA 13 42.2 47 3558.8 47 10 67 47 5.4 60 47 2EHA 20 BA 67 30.5 18.1 15 25.2 20 23.5 202.3 25.7 20 i-BMA 23.5 SMA 7 33.5 Physical Shell/core ratio 1/2 1/2 1/21/2 1/1 1/5 1/2 1/2 1/2 1/2 12/1 1/12 1/2 properties Average particle 4641 48 20 80 170 450 48 47 350 5427 1180 3187 diameter [nm] Tg ° [C.] −545 24.8 39 44.6 44.6 44.6 -60 105 44.6 44.6 44.6 44.6 Evaluation HardnessA A A A A A A A A A A B A B results Suppleness A A A A A A A A B B C D DD Softness A A A A A A A A B B C C C D Humidity resistance A A A A A A AA B B C C D B Washability A A A A A A A A A A B B B B Flaking A A A A AA B A B B D D D B Amphoteric Polymer I: YUKAFORMER AMPHOSET(manufactured by Mitsubishi Chemical Corporation) Amphoteric Polymer II:YUKAFORMER 510 (manufactured by Mitsubishi Chemical Corporation)Amphoteric Polymer III: YUKAFORMER 204WL-2 (manufactured by MitsubishiChemical Corporation) Amphoteric Polymer IV: DIAFORMER Z-632(manufactured by Mitsubishi Chemical Corporation) Amphoteric Polymer V:UNFOAMER 28-4910 (manufactured by National Starch), neutralized with2-amino-2-methyl-1-propanol in terms of an acid equivalent of 90% PVP:Polyvinylpyrrolidone (Luviskol K90 Powder, manufactured by BASF SE)

As shown in Table 1, the aqueous polymer emulsions according to theExamples had hardness, suppleness, softness, and humidity resistance.Conventionally, the hardness and the softness were hardly madecompatible with each other. As shown in Comparative Example 2, althoughthe polymer which does not have a core-shell type structure had athorough hardness, it did not exhibit softness. On the other hand, byadopting the core-shell type structure of the present invention, asshown in Examples 1 to 12, the compatibility between hardness andsoftness was realized. In consequence, the core-shell type polymerparticle of the present invention is able to form a film which is easilywashed and removed and is suitable as a hair cosmetic composition.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof. It is to be noted that thepresent application is based on a Japanese patent application filed onDec. 8, 2014 (Japanese Patent Application No. 2014-247738), and thecontents are incorporated herein by reference.

1. A core-shell type polymer particle comprising a shell part composedof an amphoteric ion polymer (A) and a core part composed of ahydrophobic polymer (B).
 2. The core-shell type polymer particleaccording to claim 1, wherein the amphoteric polymer (A) contains arepeating unit derived from an unsaturated monomer having a betainestructural group.
 3. The core-shell type polymer particle according toclaim 1, wherein the amphoteric polymer (A) contains a repeating unitderived from an unsaturated monomer having an amine oxide group.
 4. Thecore-shell type polymer particle according to claim 1, wherein theamphoteric polymer (A) contains a repeating unit derived from anunsaturated monomer having an anion group selected from the groupconsisting of a carboxyl group, a sulfonic acid group, and a phosphoricacid group, and further contains at least one of a repeating unitderived from an unsaturated monomer having a tertiary amino group and arepeating unit derived from an unsaturated monomer having a quaternaryammonium group.
 5. The core-shell type polymer particle according toclaim 1, wherein a mass ratio of the amphoteric polymer (A) to thehydrophobic polymer (B) [(A)/(B)] is 1/10 to 10/1.
 6. The core-shelltype polymer particle according to claim 1, wherein a glass transitiontemperature of the hydrophobic polymer (B) is −70° C. or higher and 105°C. or lower.
 7. The core-shell type polymer particle according to claim1, wherein the hydrophobic polymer (B) contains a structural unitderived from a hydrophobic unsaturated monomer (b), and the hydrophobicunsaturated monomer (b) contains an alkyl (meth)acrylate having ahydrocarbon chain having 1 to 45 carbon atoms.
 8. An aqueous polymeremulsion comprising the core-shell type polymer particle according toclaim 1 dispersed in water.
 9. The aqueous polymer emulsion according toclaim 8, wherein an average particle diameter of the core-shell typepolymer particle dispersed in the aqueous polymer emulsion is 10 nm to10 μm.
 10. A hair cosmetic composition comprising the aqueous polymeremulsion according to claim 8 blended therein.
 11. A hair cosmeticcomposition comprising the aqueous polymer emulsion according to claim 9blended therein.